Conventionally, an administration instrument for medical use is often used when a drug solution such as growth hormone, insulin, or the like is administered. Generally, when using the administration instrument, a doctor or a nurse performs administration in a hospital or the like, and a patient or his family performs administration at home. The administration is carried out by inserting a needle into some region on the skin, and the angle of the needle insertion into the skin and the speed of the needle insertion as well as the speed at which the drug solution is injected after the needle insertion depend on the skill level of a person who performs the administration.
FIG. 5 is a block diagram illustrating the inside of an electric injector which is currently used in dentistry. The principle of administration of drug solutions will be described with reference to FIG. 5. Now, a syringe 103 filled with a drug solution is set in a cartridge holder 104 attached to a main body 110.
When pressing a SW1, a motor 111 normally rotates, and the torque is reduced by a reduction gear box 109 which is directly connected to the motor 111 to rotate a reduction gear main-shaft 108 of the reduction gear box 109. An end of the reduction gear main-shaft 108 engages with a gear 106 through a rotary disc 107 to rotate the gear 106. Further, the gear 106 engages with a gear 105 and thereby the torque of the gear 106 propagates to the gear 105. A gear 105a is provided coaxially with the gear 105 so as to engage with a rack 104a which is provided in the lower right half of a push piston 104 from the center thereof. When the gear 105 rotates, the gear 105a also rotates in the same direction as the gear 105, and consequently, the push piston 104 is moved in the direction of the injection needle 113, whereby the drug solution in the syringe 103 is pushed out of the injection needle 113.
During injecting, air is removed in the above-described operation, and thereafter, the injection needle 113 is inserted into a target region, and the drug solution is administered. In FIG. 5, SW2 denotes a switch for reverse rotation of the motor 111, and 112 denotes a battery for driving the motor 111.
Up to this point the conventional electric injector for automatically administering a drug solution has been described.
Next, a typical administration instrument for medical use in which a drug and a drug solution are dissolved and mixed, which has conventionally been employed, will be described with reference to FIG. 6. In the administration instrument for medical use shown in FIG. 6, when it is used, a drug and a drug solution are mixed and dissolved by manual operation and then injected. In FIG. 6, constituents that are substantially identical to those shown in FIG. 5 are given the same reference numerals.
Now, a syringe 103 is set in a cartridge holder 117, and the syringe 103 contains a powder preparation 114 and a drug solution 127 which are placed in different rooms separated by a rubber 116 and a rubber 118. An injection needle 113 attached to an end of the syringe 103 is provided with a needle cap 101. In this state, the injection needle 113 is directed upward and an injection button 120 is pushed toward the injection needle 113. Then, the push piston 119 pushes the rubber 118, the rubber then pushes the drug solution 127, and the rubber 116 moves toward the injection needle 113 with the pressure at which the drug solution 127 is pushed. When the rubber 116 reaches a position slightly ahead of a protrusion 115 of the syringe, the drug solution 127 goes over the rubber 116, passes the syringe protrusion 115, and starts to flow into the room of the powder preparation 114. The injection button 120 is further pushed, and then the drug solution 127 continuously flows into the room of the powder preparation 114. After all the drug solution 127 flows into the room of the powder preparation 114, the rubber 118 contacts the rubber 116.
Next, for fully mixing and dissolving them, the injection needle 113 is directed upward in the above-mentioned state and is slightly shaken. Next, with the injection noodle 113 being directed upward, the needle cap 101 is removed and the injection button 120 is pressed, thereby releasing air. After the air releasing, the injection needle 113 is inserted into a region of the body at which the drug solution is to be administered, and the injection button 120 is pressed, whereby the drug solution is administered into the region. As described above, in the administration instrument shown in FIG. 16, the processes from the mixing and dissolving of the drug and drug solution to the administration thereof are manually performed.
However, in the conventional administration instrument for medical use, no matter how much a person is skilled in achieving the angle to the skin and the speed during needle insertion as well as the speed of injecting the drug solution and the speed of removing the needle after the needle insertion, the person who does the administration is merely a human being, and therefore, the above-mentioned angle and speeds cannot be prevented from being varied depending on the physical condition and the like at that time. Since a person who administers the drug solution and a person who is given the drug solution are both human beings, the body sizes are different and the physical conditions at the administration are not always the same. Therefore, it is difficult to administer the drug solution in the same manner every time. Therefore, it is not always possible to perform administration with reduced pain.
Particularly, since the electric injector shown in FIG. 5 is a grip type injector, the user must grip and support its body by one hand as well as keep on pressing the SW1 throughout administration. Further, since the injector is large in shape and a battery 112 is heavy in weight, a great physical strain is imposed on the person who performs administration and, therefore, it is difficult to perform self-administration using this injector.
Further, in the mixing and dissolving type administration instrument shown in FIG. 6, since the dissolving operation is manually performed, it is necessary to watch the dissolving condition with great care as well as perform the dissolving with discretion. Further, proper mixing cannot be performed unless the injection needle is shaken in a vertical orientation even after the dissolving. This is a very troublesome work for a patient having bad eyesight.
Further, a patient may have a fear about seeing the injection needle until just before administration, and this may cause a mental strain to the patient.
As described above, the needle insertion itself imposes physical and mental strains on the patient and, in some cases, seriously affects the body of the patient, which might lead to life-threatening danger.
The present invention is made to solve the above-described problems and has an object of providing an administration instrument for medical use which automatically performs needle insertion, administration, and needle removal, and further, automatically performs dissolving, mixing, and air-releasing when it is a dissolving and mixing type administration instrument, and still further, has a construction in which an injection needle is kept unseen from the outside until just before needle insertion, thereby reducing physical and mental strains on patients and realizing administration under more stable conditions.